Death is a pretty sad thing for most people. It could be death of a close friend, parents, pets, relatives and just about anyone that u have a good relationship with. People get depress and devastated. Its difficult to see the positive side.
When someone close to u die, u will know who is really the one who will stay by ur side to help u. To help u through the tough time. And for some culture, they celebrate the death of someone. So instead of mourning the death, they celebrate the person life. This is the most positive point to think about. And a song that really relates to this is Eminem - You're Never Over
